Friction material, such as a disk brake pad and brake lining, is used for a car, railroad vehicles, and various industrial machines for the braking.
Friction materials currently used, such as disk brake pad, mainly comprise a Non-Asbestos-Organic (hereinafter abbreviated to as “NAO material”) series disk brake pad using fibrous material such as Aramid fiber, mineral fiber, etc., and a friction regulating agent such as cashew dust, carbon black, etc., which causes less squeal noise or abnormal sound at the time of braking (see Japanese Unexamined Patent Publication No. Hei. 6-184525, pages 1 to 3).
However, characteristics required for the brake tend to be heightened more and more in recent years, and improvement in effectiveness of brake is particularly required for the conventional NAO materials. According to the conventional disk brake pad as mentioned above, however, heat resistance is insufficient and there are defects that effectiveness of brake is likely lowered (including fade phenomenon) under high load, high speed, high temperature, etc.
The present invention is to provide a friction material composition which is suitable for a friction material, which shows less lowering in effectiveness of brake under high load, high speed, high temperature, etc., and controlling abrupt increase in friction coefficient at initial brake after allowing an automobile to stand for a period of time.
Also, the present invention is to provide a friction material, which is less lowering in effectiveness of brake under high load, high speed, high temperature, etc., and controlled in abrupt increase of friction coefficient at initial brake after allowing an automobile to stand for a period of time.